This article builds a theory of financial system architecture. We ask: what is a financial market, what is a bank, and what determines the economic role of each? Starting with basic assumptions about primitives—the types of agents and the nature of informational asymmetries—we provide a theory that explains which agents coalesce to form banks and which trade in the capital market. It is shown that borrowers of higher observable qualities access the financial market. Moreover, a financial system in its infancy will be bank-dominated, and increased financial market sophistication diminishes bank lending.

In this article, we provide a novel rationale for credit ratings. The rationale that we propose is that credit ratings serve as a coordinating mechanism in situations where multiple equilibria can obtain. We show that credit ratings provide a “focal point” for firms and their investors, and explore the vital, but previously overlooked implicit contractual relationship between a credit rating agency (CRA) and a firm through its credit watch procedures. Credit ratings can help fix the desired equilibrium and as such play an economically meaningful role. Our model provides several empirical predictions and insights regarding the expected price impact of rating changes.

How will banks evolve as competition increases from other banks and from the capital market? Will banks become more like capital market underwriters and offer passive transaction loans or return to their roots as relationship lending experts? These are the questions we address. Our key result is that as interbank competition increases, banks make more relationship loans, but each has lower added value for borrowers. Capital market competition reduces relationship lending (and bank lending shrinks), but each relationship loan has greater added value for borrowers. In both cases, welfare increases for some borrowers but not necessarily for all.

We explain why an issuer may wish to raise external capital by selling multiple financial claims that partition its total asset cash flows, rather than a single claim. We show that, in an asymmetric information environment, the issuer's expected revenue is enhanced by such cash flow partitioning because it makes informed trade more profitable. This approach seems capable of shedding light on corporate incentives to issue debt and equity, as well as on financial intermediaries' incentives to issue multiple classes of claims against portfolios of securitized assets.

We point to the vast empirical literature in banking to argue that the current expansion of scale and scope in banking represents a puzzle. We then present two explanations that help us to understand why banks are getting bigger and doing more. Our explanations suggest that banks may be doing this to increase their shareholders' wealth and/or merely to enhance the reputation of their management (CEOs). The latter could lead to herd behavior involving banks that increase size and scope despite a dissipation of shareholders' wealth. Alternatively, increasing size and scope may offer strategic benefits (and hence increase shareholder wealth) in an environment with sufficient profitability in current operations and substantial uncertainty about future core competencies. We explore conditions under which either one of these competing explanations may dominate.

We focus on public‐market investor participation to analyze the firm's decision to stay public or go private. The liquidity of public ownership is both a blessing and a curse: It lowers the cost of capital, but also introduces volatility in a firm's shareholder base, exposing management to uncertainty regarding shareholder intervention in management decisions, thereby affecting the manager's perceived decision‐making autonomy and curtailing managerial inputs. We extract predictions about how investor participation affects stock price level and volatility and the public firm's incentives to go private, providing a link between investor participation and firm participation in public markets.